If Critical Mass was a parade, there would be someone able to tell you its route. Before the ride finishes.

Also, by most definitions, people would be marching.

• a ceremonial procession including people marching
• walk ostentatiously; "She parades her new husband around town"
• an extended (often showy) succession of persons or things; "a parade of strollers on the mall"; "a parade of witnesses"
• march in a procession; "the veterans paraded down the street"
• a visible display; "she made a parade of her sorrows"
  wordnetweb.princeton.edu/perl/webwn

It's definitely not a parade.